T-Mobile USA has restored voice and data services to users after an eight-hour outage that affected nearly 1.7 million subscribers.

"T-Mobile confirms it has fully restored voice and text/picture messaging services for customers affected by intermittent service disruptions on Tuesday," the company said in a statement posted on Wednesday at 1:25 a.m., Eastern time.

"Our sole focus has been restoring full services for all customers; we are now investigating the root cause of the incident," it said.

The outage, which began around 5:30 p.m. on Tuesday, disrupted voice and some data services for 5 percent of T-Mobile's customers in various areas. Based on the 33.5 million subscribers that T-Mobile reported at the end of the second quarter, the outage affected nearly 1.7 million people.